The present invention relates generally to data processing and, in particular, to injection of at least a partial cache line into a multilevel cache hierarchy.
A conventional multiprocessor (MP) computer system, such as a server computer system, includes multiple processing units all coupled to a system interconnect, which typically comprises one or more address, data and control buses. Coupled to the system interconnect is a system memory, which represents the lowest level of volatile memory in the multiprocessor computer system and which generally is accessible for read and write access by all processing units. In order to reduce access latency to instructions and data residing in the system memory, each processing unit is typically further supported by a respective multi-level cache hierarchy, the lower level(s) of which may be shared by one or more processor cores.
Cache memories are commonly utilized to temporarily buffer memory blocks that might be accessed by a processor in order to speed up processing by reducing access latency introduced by having to load needed data and instructions from system memory. In some MP systems, the cache hierarchy includes at least two levels. The level one (L1) or upper-level cache is usually a private cache associated with a particular processor core and cannot be accessed by other cores in an MP system. Typically, in response to a memory access instruction such as a load or store instruction, the processor core first accesses the directory of the upper-level cache. If the requested memory block is not found in the upper-level cache, the processor core then accesses lower-level caches (e.g., level two (L2) or level three (L3) caches) or system memory for the requested memory block.